Stellar Population Effects on the Inferred Photon Density at Reionization

The relationship between stellar populations and the ionizing flux with which they irradiate their surroundings has profound implications for the evolution of the intergalactic medium. We quantify the ionizing flux arising from synthetic stellar populations which incorporate the evolution of interacting binary stars. We determine that these show ionizing flux boosted by 60 per cent at 0.05 < Z < 0.3 Z_sun and a more modest 10-20 per cent at near-Solar metallicities relative to star-forming populations in which stars evolve in isolation. The relation of ionizing flux to observables such as 1500A continuum and ultraviolet spectral slope is sensitive to attributes of the stellar population including age, star formation history and initial mass function. For a galaxy forming 1 M_sun yr^{-1}, observed at > 100 Myr after the onset of star formation, we predict a production rate of photons capable of ionizing hydrogen, N_ion = 1.4 x 10^{53} s^{-1} at Z = Z_sun and 3.5 x 10^{53} s^{-1} at 0.1 Z_sun, assuming a Salpeter-like initial mass function. We evaluate the impact of these issues on the ionization of the intergalactic medium, finding that the known galaxy populations can maintain the ionization state of the Universe back to z ~ 9, assuming that their luminosity functions continue to M_UV = -10, and that constraints on the intergalactic medium at z ~ 2 - 5 can be satisfied with modest Lyman continuum photon escape fractions of 4 - 24 per cent depending on assumed metallicity.Comment: 17 pages, accepted by MNRAS. BPASS models can be found at http://bpass.auckland.ac.nz

Thermophysical and chemical characterization of charring ablative materials Final report

Thermophysical and chemical properties of charring ablative material

The type IIb SN 2008ax: the nature of the progenitor

A source coincident with the position of the type IIb supernova (SN) 2008ax is identified in pre-explosion Hubble Space Telescope (HST) Wide Field Planetary Camera 2 observations in three optical filters. We identify and constrain two possible progenitor systems: (i) a single massive star that lost most of its hydrogen envelope through radiatively driven mass loss processes, prior to exploding as a helium-rich Wolf-Rayet star with a residual hydrogen envelope, and (ii) an interacting binary in a low mass cluster producing a stripped progenitor. Late time, high resolution observations along with detailed modelling of the SN will be required to reveal the true nature of this progenitor star.Comment: 5 pages, 2 figures, resolution of figure 1 reduced, figure 2 revised, some revision following referee's comments, accepted for publication in MNRAS letter

Phonon anomalies due to strong electronic correlations in layered organic metals

We show how the coupling between the phonons and electrons in a strongly correlated metal can result in phonon frequencies which have a non-monotonic temperature dependence. Dynamical mean-field theory is used to study the Hubbard-Holstein model that describes the \kappa-(BEDT-TTF)_2 X family of superconducting molecular crystals. The crossover with increasing temperature from a Fermi liquid to a bad metal produces phonon anomalies that are consistent with recent Raman scattering and acoustic experiments.Comment: 6 pages, 3 eps figure

Study to assess the effect of a structured communication approach on quality of life in secure mental health settings (Comquol): study protocol for a pilot cluster randomized trial

Background Forensic mental health services have largely ignored examining patients’ views on the nature of the service offered to them. A structured communication approach (DIALOG) has been developed with the aim of placing the patient’s perspective of their care at the heart of the discussions between patients and clinicians. The effectiveness of the structured communication approach in community mental health services has been demonstrated but no trial taken place in a secure psychiatric setting. This pilot study is evaluating a six-month intervention combining DIALOG with principles of Solution Focused Therapy (SFT) on quality of life in medium secure settings. Methods/design A cluster randomized controlled trial design is being employed to conduct a 36 months pilot study. Participants are recruited from six medium secure in–patient services with 48 patients in the intervention group and 48 in the control group. The intervention uses a structured communication approach. It comprises of six meetings between patient and nurse over held once a month a six month period. During each meeting patients rate their satisfaction with a range of life and treatment domains with responses displayed on a tablet. The rating is followed by a discussion on how to improve the current situation in those domains identified by the patient. Assessments take place prior to the intervention (baseline), at 6 months (post intervention) and at 12 months (follow-up). The primary outcome is self reported Quality of Life. Discussion: The study aims to a) establish the feasibility of the trial design as the basis for determining the viability of a large full-scale trial, b) determine the variability of the outcomes of interest (quality of life, levels of satisfaction, disturbance, ward climate, and engagement with services) c) estimate the costs of the intervention and d) refine the intervention following the outcome of the study based upon the experiences of the nurses and patients. The intervention allows patients to have a greater say in how they are treated and targets care on areas that patients identify as important to them. It is intended to establish systems that support meaningful patient (and carer) involvement and participation. Trial registration: Current Controlled Trials ISRCTN34145189 Keywords: Comquol, DIALOG, Forensic, Mental Health, Quality of Life, Solution Focused Brief Therapy

\u3cem\u3eBromus tectorum\u3c/em\u3e Litter Alters Photosynthetic Characteristics of Biological Soil Crusts from a Semiarid Shrubland

Invasion by the exotic annual grass Bromus tectorum has increased the cover and connectivity of fine litter in the sagebrush steppes of western North America. This litter tends to cover biological soil crusts, which could affect their metabolism and growth. To investigate this possible phenomenon, biological soil crusts dominated by either the moss Bryum argenteum or the lichen Diploschistes muscorum were covered with B.tectorum litter (litter treatment) or left uncovered (control treatment) and exposed to natural field conditions. After periods of five and ten months, we removed the litter and compared the photosynthetic performance of biological soil crusts from the two treatments. Litter induced photosynthetic changes in our samples. In bothB. argenteum and D. muscorum, biological soil crusts that had been covered with litter for ten months had lower rates of gross photosynthesis and lower chlorophyll content than control samples. Similarly in both biological soil crust types, litter reduced the rate of dark respiration. For D. muscorum, the reduction in dark respiration fully compensated for the decrease in gross photosynthesis, resulting in similar values of net photosynthesis in the two treatments. In contrast, for B. argenteum, net photosynthesis was four-times greater in the control than the litter treatment. Also under litter cover, D. muscorum showed three common adaptations to shade conditions: a decrease in the light compensation point, in the light intensity needed to achieve 95% of maximal net photosynthesis, and in the chlorophyll a/b ratio. None of these changes was apparent in B. argenteum. Overall, our results indicate that photosynthetic responses to the presence of litter varied among species of the crust biota and that the litter can reduce the photosynthetic capacity of biological soil crusts. These results help to explain field observations of decreases in biological soil crust cover and changes in biological soil crust composition with increases in litter cover, and suggest that the landscape-wide invasion by B. tectorum may have substantial effects on biological soil crust performance and therefore their capacity to function in semiarid shrublands

iPTF15eqv: Multi-wavelength Expos\'e of a Peculiar Calcium-rich Transient

The progenitor systems of the class of "Ca-rich transients" is a key open issue in time domain astrophysics. These intriguing objects exhibit unusually strong calcium line emissions months after explosion, fall within an intermediate luminosity range, are often found at large projected distances from their host galaxies, and may play a vital role in enriching galaxies and the intergalactic medium. Here we present multi-wavelength observations of iPTF15eqv in NGC 3430, which exhibits a unique combination of properties that bridge those observed in Ca-rich transients and Type Ib/c supernovae. iPTF15eqv has among the highest [Ca II]/[O I] emission line ratios observed to date, yet is more luminous and decays more slowly than other Ca-rich transients. Optical and near-infrared photometry and spectroscopy reveal signatures consistent with the supernova explosion of a < 10 solar mass star that was stripped of its H-rich envelope via binary interaction. Distinct chemical abundances and ejecta kinematics suggest that the core collapse occurred through electron capture processes. Deep limits on possible radio emission made with the Jansky Very Large Array imply a clean environment ($n <$ 0.1 cm$^{-3}$) within a radius of $\sim 10^{17}$ cm. Chandra X-ray Observatory observations rule out alternative scenarios involving tidal disruption of a white dwarf by a black hole, for masses > 100 solar masses). Our results challenge the notion that spectroscopically classified Ca-rich transients only originate from white dwarf progenitor systems, complicate the view that they are all associated with large ejection velocities, and indicate that their chemical abundances may vary widely between events.Comment: 24 pages, 16 figures. Closely matches version published in The Astrophysical Journa

Night Matters—Why the Interdisciplinary Field of “Night Studies” Is Needed

The night has historically been neglected in both disciplinary and interdisciplinary research. To some extent, this is not surprising, given the diurnal bias of human researchers and the difficulty of performing work at night. The night is, however, a critical element of biological, chemical, physical, and social systems on Earth. Moreover, research into social issues such as inequality, demographic changes, and the transition to a sustainable economy will be compromised if the night is not considered. Recent years, however, have seen a surge in research into the night. We argue that “night studies” is on the cusp of coming into its own as an interdisciplinary field, and that when it does, the field will consider questions that disciplinary researchers have not yet thought to ask

Bolometric light curves and explosion parameters of 38 stripped-envelope core-collapse supernovae

Literature data are collated for 38 stripped-envelope core-collapse supernovae (SE SNe; i.e. SNe IIb, Ib, Ic and Ic-BL) that have good light curve coverage in more than one optical band. Using bolometric corrections derived in previous work, the bolometric light curve of each SN is recovered and template bolometric light curves provided. Peak light distributions and decay rates are investigated; SNe subtypes are not cleanly distinguished in this parameter space, although some grouping of types does occur and there is a suggestion of a Phillips-like relation for most SNe Ic-BL. The bolometric light curves are modelled with a simple analytical prescription and compared to results from more detailed modelling. Distributions of the explosion parameters shows the extreme nature of SNe Ic-BL in terms of their 56Ni mass and the kinetic energy, however ejected masses are similar to other subtypes. SNe Ib and Ic have very similar distributions of explosion parameters, indicating a similarity in progenitors. SNe~IIb are the most homogeneous subtype and have the lowest average values for 56Ni mass, ejected mass, and kinetic energy. Ejecta masses for each subtype and SE SNe as a whole are inconsistent with those expected from very massive stars. The majority of the ejecta mass distribution is well described by more moderately massive progenitors in binaries, indicating these are the dominant progenitor channel for SE SNe